Curable compositions

ABSTRACT

ROOM TEMPERATURE VULCANIZING SILICONE ELASTOMERS ARE PREPARED BY THE ADDITION OF A NOVEL CROSS-LINKING AGENT SUCH AS ACETOXYPROPENYLENYLTRIACETOXYSILANE TO A SILANOL CHAIN-STOPPED POLYDIORGANOSILOXANE FLUID. THESE COMPOSITIONS ARE STABLE, FREE FLOWING FLUIDS IN THE ABSENCE OF MOISTURE BUT CURE TO A RUBBERY, SOLID ELASTIC STATE UPON EXPOSURE TO MOISTURE. THESE COMPOSITONS ARE PARTICULARLY USEFUL AS ADHESIVES IN DIFFCULT BONDING SITUATIONS SUCH AS ATTACHING GLASS WINDOW PANES TO ALUMINUM WINDOW FRAMES.

United States Patent O1 hoe 3,661,817 Patented May 9, 1972 3,661,817CURABLE COMPOSITIONS Stephen B. Hamilton, Schenectady, Melvin D. Beers,Ballston Lake, and Abe Berger and Terry G. Selin, Schenectady, N.Y.,assignors to General Electric Company, New York, N.Y. No Drawing. FiledMay 4, 1970, Ser. No. 34,576 Int. Cl. C08h 9/00 U.S. Cl. 260-18 S 46Claims ABSTRACT OF THE DISCLOSURE Room temperature vulcanizing siliconeelastomers are prepared by the addition of a novel cross-linking agentsuch as acetoxypropenylenyltriacetoxysilane to a silanol chain-stoppedpolydiorganosiloxane fluid. These compositions are stable, free flowingfluids in the absence of moisture but cure to a rubbery, solid elasticstate upon exposure to moisture. These compositions are particularlyuseful as adhesives in difficult bonding situations such as attachingglass window panes to aluminum window frames.

BACKGROUND OF THE INVENTION This invention pertains to fluidorganopolysiloxanes which are capable of vulcanizing at room temperatureto rubbery materials, to the cross-linking agents used in suchcompositions, and to the process of making the vulcanizable materials.

The prior art cross-linking agents which have found greatest commercialsuccess are either solid at room temperature or unstable at roomtemperature and their use may result in products which are lacking inadhesion to particular substrates. A disadvantage of the prior artcross-linking systems which are solid at room temperature is that theymust be heated to the liquid state prior to use. This necessitates anextra step in the manufacture of sealants utilizing this type ofcross-linking agent and requires that all storage tanks and lines usedto carry this agent be heated. Serious problems occasionally result whenthe heating element of one of the tanks or lines is defective and thecross-linking agent is allowed to crystallize. Considerable product thatis deficient in crosslinking agent may be produced and packaged andequipment time, personnel time and product are lost.

The cross-linking agents which are unstable at room temperature must bemaintained under refrigeration prior to use. Failure to maintain thematerials under refrigeration results in disproportionation and, again,a product lacking in the desired properties.

The lack of adhesion of particular prior art sealants to particularsubstrates has also resulted in problems. For example, when glass issealed into aluminum window frames, a defective bond between thealuminum and the sealant results in water leakage between the aluminumwindow frame and the glass mounted therein.

The prior art cross-linking systems are exemplified by the disclosurescontained in US. Pat. 3,035,016 of Bruner which issued in 19 62 and US.Pat. 3,296,195 of Goossens which issued in 1967. While these disclosedmaterials have enjoyed a measure of commercial success, they have notbeen completely successful in solving the problems of handling whichwere described.

SUMMARY OF THE INVENTION In accordance with this invention there areprovided organopolysiloxanes comprising a silanol chain-stoppedpolydiorganosiloxane, and at least one silane of the formula,

wherein R and R are at least one radical having not more than about 8carbon atoms selected from the group consisting of hydrocarbyl,halohydrocarbyl, nitrohydrocarbyl, alkoxyhydrocarbyl and cyano loweralkyl and can be different; R and R are at least one radical having notmore than about 8 carbon atoms selected from the group consisting ofhydrocarbyl and halohydrocarbyl and can be different; R is at least oneunsaturated radical having a valence of at least two and from about 3 toabout 8 carbon atoms selected from the group consisting of divalent andtrivalent unsaturated hydrocarbon radicals, and halo andalkoxy-substituted divalent and trivalent unsaturated hydrocarbonradicals; a is an integer of one through 3, b is a whole number of 0through 2, c is a While number of 0 through 2, d is an integer of onethrough 3 and e is an integer of one through 2 and the sum of a, b, cand d is 4.

It has been discovered that when acetoxyalkenyl-substituted silanes ofFormula 1 are used as cross-linking agents for or as agents to defercross-linking of silanol chain-stopped polydiorganosiloxane that theheating requirements, refrigeration requirements and lack of adhesionproblems inherent in the manufacture and use of prior art materials nolonger exist. The acetoxyalkenylsubstituted silanes are fluid and stableat room temperature and permit the production of sealants which havesignificantly improved adhesion to substrates when cured.

DESCRIPTION OF PREFERRED EMBODIMENTS In the description the followingdefinitions and terms apply unless otherwise specified. The termhydrocarbyl as used herein means a hydrocarbon from which one hydrogenatom has been removed, i.e., a monovalent hydrocarbon radical, theabbreviation RTV as used herein means a room temperature vulcanizablematerial.

A silanol chain-stopped polydiorganosiloxane useful in an RTVcomposition of this invention may be represented by the formula,

I R5 floral wherein R and R are each organic radicals of not more than 8carbon atoms selected from the group consisting of hydrocarbyl,halohydrocarbyl, and cyano lower alkyl and n is a number from about 5 toabout 15,000 or more.

The silanol chain-stopper polydiorganosiloxanes are well known in theart and include compositions containing different R and R groups. Forexample, the R groups can be methyl while the R groups can be phenyland/or beta-cyanoethyl. Furthermore, within the scope of the definitionof polydiorganosiloxanes useful in this invention are copolymers ofvarious types of diorganosiloxane units, such as silanol chain-stoppedcopolymers of dimethylsiloxane units, diphenylsiloxane units andmethylphenylsiloxane units or, for example, copolymers ofdimethylsiloxane units, methylphenylsiloxane units andmethylvinylsiloxane units. Preferably, at least 50% of the R and Rgroups of the silanol chain-stopped polydiorganosiloxanes are methylgroups.

A mixture of various silanol chain-stopped polydiorganosiloxanes alsomay be employed. The silanol chainstopped materials useful in the RTVcompositions of this invention have been described aspolydiorganosiloxanes but such materials can also contain minor amounts,e.g., up to about 20% of monoorganosiloxane units such asmonoalkylsiloxane units, e.g., monomethylslloxane units andmonophenylsiloxane units. The technology involved in incorporatingmonoalkylsiloxane units into RTV compositions is disclosed in US. Pat.3,382,205 of Beers (1968), which is hereby incorporated into the presentapplication by reference. The silanol chainstopped materials may alsocontain triorganosiloxane units, such as trialkylsiloxane units, e.g.,trimethylsiloxane units, tributylsiloxane units and triphenylsiloxaneunits. The silanol chain-stopped materials may also containtalkoxysiloxane units, e.g., t-butoxysiloxane units, t-pentoxysiloxaneunits, and t-amyloxysiloxane units. Efiective results can be obtained ifsufiicient t-alkoxysiloxane is utilized in combination with thesilanol-terminated polydiorganosiloxane of Formula 2 to provide apolymer having a ratio of t-alkoxysiloxane units to silanol of 0.(} to0.9 and preferably 0.2 to 0.8 tert-alkoxydialkylsiloxy units persilanol. Many of the t-alkoxysiloxanes useful as part of the silanolchain-stopped materials are described and claimed in US. Pat. 3,438,930of Beers, which issued Apr. 15, 1969 and is assigned to the GeneralElectric Company, the disclosure of which is expressly incorporatedherein by reference.

The silanol chain-stopped polydiorganosiloxanes employed in the practiceof the present invention may vary from low viscosity thin fluids toviscous gums, depending upon the value of n and the nature of theparticular organic groups represented by R and R In the above Formula 1R and R may be, for example, aryl, such as phenyl, benzyl, tolyl, xylyland ethylphenyl; halogen-substituted aryl, such as 2,6-di-chlorophenyl,4- bromophenyl, 2,5-di-fluorophenyl, 2,4,6 trichlorophenyl and2,5-dibromophenyl; nitro-substituted aryl, such as 4- nitrophenyl and2,6-di-nitrophenyl; alkoxy-substitilted aryl, such as 4-methoxyphenyl,2,6-dimethoxyphenyl, 4- t-butoxyphenyl, 2-ethoxyphenyl, and2,4,6-trimethoxyphenyl; alkyl, such as methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, amyl, hexyl,heptyl, octyl, and the various homologs and isomers of alkyl of not morethan about 8 carbon atoms; alkenyl such as vinyl, allyl, n-butenyl-l,n-butenyl-Z, n-pentenyl- 2, n-hexenyl-Z, 2,3 dimethylbutenyl 2, nheptenyl, noctenyl, and the various homologs and isomers of alkenyl ofnot more than about 8 carbon atoms; alkynyl such as propargyl, 2-butynyland the various homologs and isomers of alkynyl of not more than about 8carbon atoms; haloalkyl such as chloromethyl, iodomethyl, bromomethyl,fluoromethyl, chloroethyl, iodoethyl, bromoethyl, fluoroethyl,trichloromethyl, diiodoethyl, tribromomethyl, trifluoromethyl,dichloroethyl, chloro-n-propyl, bromo-npropyl, iodoisopropyl,bromo-n-butyl, bromo-tert-butyl, 1,3,3-trichlorobutyl, chloropentyl,bromopentyl, 2,3-dichloropentyl, 3,3-dibromopentyl, chlorohexyl,bromohexyl, 2,4 dichlorohexyl, 1,3 dibromohexyl, 1,3,4 trichlorohexyl,chloroheptyl, bromoheptyl, fluoroheptyl, 1,3- dichloroheptyl,1,4,4-trichloroheptyl, 2,4-dichloromethylheptyl, chlorooctyl,bromooctyl, iodooctyl, 2,4 dichloromethylhexyl, 2,4-dichlorooctyl, 2,4,4trichloromethylpentyl, 1,3,5-tribromooctyl and the various homologs andisomers of haloalkyl of not more than about 8 carbon atoms; haloalkenylsuch as chlorovinyl, bromovinyl, chloroallyl, bromoallyl,3-chloro-n-butenyl-1,3 chloro-npentenyl-l, 3-fluoro-n-heptenyl 1, 1,3,3trichloro nheptenyl-S, l,3,5-trichloro-n-octenyl 6, 2,3,3trichloromethylpentenyl-4 and the various homologs and isomers ofhaloalkenyl of not more than about 8 carbon atoms; haloalkynyl such aschloropropargyl, bromopropargyl and the various homologs and isomers ofhaloalkynyl of not more than about 8 carbon atoms; nitroalkyl such asnitromethyl, nitroethyl, nitro-n-propyl, nitro n butyl, nitropentyl,1,3-dinitroheptyl and the homologs and isomers of nitroalkyl of not morethan about 8 carbon atoms; nitroalkenyl such as nitroallyl,3-nitro-n-butenyl- 1, 3-nitro-n-heptenyl-l, and the various homologs andisomers of nitroalkenyl of not more than about 8 carbon atoms;nitroalkynyl such as nitropropargyl and the various homologs and isomersof nitroalkynyl of not more than about 8 carbon atoms; alkoxyalkyl andpolyalkoxyalkyl such as methoxymethyl, ethoxymethyl, butoxymethyl,methoxyethyl, ethoxyethyl, ethoxyethoxyethyl, methoxyethoxymethyl,butoxymethoxyethyl, ethoxybutoxyethyl, methoxypropyl, butoxypropyl,methoxybutyl, butoxybutyl, methoxypentyl, butoxypentyl,methoxymethoxypentyl, butoxyhexyl, methoxyheptyl, ethoxyethoxy and thevarious homologs and isomers of alkoxyalkyl and polyalkoxyalkyl of notmore than about 8 carbon atoms; alkoxyalkenyl and polyalkoxyalkenyl suchas ethoxyvinyl, methoxyallyl, butoxyallyl, methoxy-n-butenyl-l,butoxyn-pentenyl-l, methoXyethoxy-n-heptenyl-1, and the various homologsand isomers of alkoxyalkenyl and polyalkoxyalkenyl of not more thanabout 8 carbon atoms; alkoxyalkynyl and polyalkoxyalkynyl such asmethoxypropargyl and the various homologs and isomers of alkoxyalkynyland polyalkoxyalkynyl of not more than about 8 carbon atoms; cycloalkyl,cycloalkenyl and alkyl, halogen, alkoxy and nitro-substituted cycloalkyland cycloalkenyl such as cyclopentyl, cyclohexyl, cycloheptyl,cyclooctyl, cyclononyl, 6-methylcyclohexyl, 2,5-dimethylcycloheptyl,4-butylcyclopentyl, 3,4-dichlorocyclohexyl, 2,6-dibromocycloheptyl,6-methoxycyclooctyl, 2-nitrocyclopentyl, l-cyclopentenyl,3-methyl-l-cyclopentenyl, 5- methoxy-l-cyclopentenyl, 3,4-dimethy1-1cyclopentenyl, 2,5-dimethoxy-l-cyclopentenyl, S-methyl-S-cyclopentenyl,3,4-dichloro-5-cyclopentenyl, 5-(tert-butyl)-1 cyclopentenyl,2-nitro-1-cyclohexenyl, l-cyclohexenyl, 3-methy1-1- cyclohexenyl,3,4-dimethyl 1 cyclohexenyl and 6-methoxy-l-cyclohexenyl; and cyanolower alkyl such as cyanomethyl, beta-cyanoethyl, gamma-cyanopropyl,deltacyanobutyl and gamma-cyanoisobutyl.

In Formula 1, R and R may be hydrocarbyl and halohydrocarbyl such asthose listed above for R and R Examples of divalent and trivalentunsaturated radicals represented by R present in the compositions ofthis invention are, for example,

p wm-ii-onsr-on-om-o-i-Q Other examples are readily apparent from thedescription of the substituents which may be present on the silane.

The RTV composition of this invention may be prepared simply by admixingone or more of the silanes of Formula 1, having an awerage of at leastabout 2.05 silicon-bonded acyloxy radicals per silicon atom with thesilanol chain-stopped polydiorganosiloxane. The components arepreferably at room temperature during mixing. Since the silane tends tohydrolyze upon contact with moisture, care should be exercised toexclude moisture during the addition of the silane to the silanolchain-stopped polydiorganosiloxane. Likewise, care should be taken thatthe mixture of the silane and the silanol chain-stoppedpolydiorganosiloxane is maintained under substantially anhydrousconditions if it is desired to store the admixture for an extendedperiod of time prior to conversion of the composition to the cured,solid, elastic silicone rubber state. On the other hand if it is desiredto permit the mixture to cure immediately upon admixture of the silaneand the polydiorganosiloxane, no special precautions are necessary andthe two components may be mixed and placed in the form or shape which isdesired for the cured composition.

The amount of the silane admixed with the silanol chain-stoppedpolydiorganosiloxane may vary within wide limits; however, for bestresults, it is preferred to add an excess of one mole of the silane permole of silanol groups in the silanol chain-stopedpolydiorganosiloxanes. Satisfactory curing may be obtained, for example,with from about 1.0 to about 4 moles of the silane per mole of silanolgroups in the polydiorganosiloxane. No particular benefit is derivedfrom using more than 4 moles of the silane per mole of thepolydiorganosiloxane.

The admixture may be carried out in the presence of an inert solvent,i.e., a solvent which will not react with the silanol, alkoxy or acyloxygroups on the silicon; and suitable solvents include hydrocarbonsolvents such as benzene, toluene, xylene or petroleum ethers;halogenated solvents such as perchloroethylene or chlorobenzene andorganic ethers such as diethylether and dibutylether; ketones such asmethylisobutylketone and fluid, hydroxylfree polysiloxanes. The presenceof a solvent is particularly advantageous when the silanol chain-stoppedpolydiorganosiloxane used in a high molecular weight gum. The solventreduces the overall viscosity of the composition. RTV compositionsprepared in solvent solution may be stored in the absence of moisture insolution until used. This is particularly valuable when a high viscosityor gummy composition is to be employed in a coating or other similarapplication.

Adhesion to various substrates containing an oxide film may be improvedby the addition of a di-t-alkoxydiacetoxysilane to an RTV composition ofthis invention. The technology involved in the addition of this type ofmaterial is disclosed in US. Pat. 3,296,161 of Kulpa, which is herebyincorporated by reference.

The RTV compositions of this invention are stable for substantialperiods in the absence of moisture. Consequently they can be stored forprolonged periods of time without deleterious effect. During properstorage no significant change occurs in the physical properties of theRTV compositions. This is of particular importance from a commercialstandpoint, since it assures that once an RTV composition is preparedwith a certain consistency and cure time that neither will changesignificantly upon storage. Storage stability is one of thecharacteristics which takes the compositions of this inventionparticularly valuable as a one component room temperature vulcanizingcomposition.

A wide choice of components is available in the preparation of an RTVcomposition of this invention. In general, the particular componentsemployed are a function of the properties desired in the cured siliconerubber.

Thus, with a particular silane some variation in the properties of thecured silicone rubber are obtained by varying the molecular weight (asmeasured indirectly by 'viscosity) of the silanol chain-stoppedpolydiorganosiloxane. For a given system, as the viscosity of thesilanol chainstopped starting material increases, the hardness of thecured rubber decreases while the elongation increases. On the otherhand, with a lower viscosity material, generally, the linear polymerchains are shorter and more crosslinking is effected resulting in acured rubber having a lower elongation and increased hardness.

An RTV composition is prepared in accordance with this invention bymixing an acetoxyalkylpolyacetoxysilane with a silanol chain-stoppedpolydiorganosiloxane. The RTV may be used without further modificationin many sealing, caulking or coating applications by merely placing thecomposition in the desired place and permitting it to cure upon exposureto the moisture present in the atmosphere. Upon exposure of suchcompositions to atmospheric moisture, even after storage for times aslong as two years or more, a skin will form on the compositions shortlyafter exposure and cure to the rubbery state will occur within 12 to 24hours, all at room temperature.

The time required for the formation of such skin may.

vary from a minimum of about to minutes to a maximum of about 1 hour.

It is often desirable to modify the RTV composition of the presentinvention by the addition of various materials which act as extenders orwhich change various properties such as cure rate and color. Forexample, if it is desired to reduce the time required for complete cureby a factor of about 2. to 5, the composition may be modified by theincorporation of a minor amount of a carboxylic acid salt and/orchelates of a metal ranging from lead to manganese, inclusive, in theelectromotive series of metals. Particular metals included are lead,tin, nickel, cobalt, iron, cadmium, chromium, zinc and manganese.Carboxylic acids from which the salts of these metals may be derived aremonocarboxylic acids or dicarboxylic acids and the metallic salts may beeither soluble or insoluble in the silanol chain-stoppedpolydiorganosiloxane used. Preferably, the salts employed are soluble inthe silanol chain-stopped polydiorganosiloxane since this facilitatesthe uniform dispersion of the salt in the reaction mixture.

Illustrative of metal salts which may be employed are, for example, zincnaphthenate, lead naphthenate, cobalt naphthenate, iron 2-ethylhexoate,cobalt octoate, zinc octoate, lead octoate, chromium octoate and tinoctoate. Operative metal salts also include those in which the metallicion contains a hydrocarbon substituent, such as, for example,carbomethoxyphenyl tin tris-uberate, isobutyl tin triceroate,cyclohexenyl lead triactotinate, xenyl lead tris-alicylate, dimethyl tindibutyrate, basic dimethyl tin oleate, dibutyl tin diacetate, dibutyltin dilaurate, divinyl tin diacetate, dibutyl tin dibenzoate, dibutyltin dioctoate, dibutyl tin maleate, dibutyl tin adipate, diisoamyl tinbis-trichlorobenzoate, diphenyl lead diformate, dibutyl tin dilacetate,dicyclopentyl lead bis-monochloroacetate, dibenzyl lead di-Z-pentanoate,diallyl lead di-2- hexenoate, triethyl tin tartrate, tributyl tinacetate, triphenyl tin acetate, tricyclohexyl tin acrylate, tritolyl tinterephthalate, tri-n-propyl lead acetate, tristearyl lead succinate,trinaphthyl lead p-methylbenzoate, tris-phenyl lead cyclohexenylacetate, triphenyl lead ethylmalonate, etc.

The amount of the metal salt of the organic carboxylic acid which may beemployed generally is a function of the increased rate of curing desiredso that any amount of such salt up to a maximum effective amount forincreasing the cure rate may be employed. In general, no particularbenefit is derived from employing more than about 5% by weight of such ametal salt based on the weight of the silanol chain-stoppedpolydiorganosiloxane. Preferably, where such metal salt is employed, itis present in an amount equal to from about 0.01% to 2.0% by weight,based on the weight of the polydiorganosiloxane.

Metal chelates such as those disclosed in US. Pats. 3,334,067 and3,065,194 may also be used in the RTV composition of this invention ascatalysts in amounts from about 0.01 part to about 10 parts based onparts of the silanol chain-stopped polydiorganosiloxane.

The RTV compositions of the present invention may be varied also by theincorporation of various extenders or fillers. Illustrative of the manyfillers which may be employed with the composition of the presentinvention are titanium dioxide, lithopone, zinc oxide, zirconiumsilicate, silica aerogel, iron oxide, diatomaceous earth, calciumcarbonate, fumed silica, silazane treated silica, precipitated silica,glass fibers, magnesium oxide, chromic oxide, zirconium oxide, aluminumoxide, crushed quartz, calcined clay, asbestos, carbon, graphite, cork,cotton, synthetic fibers, etc. Silazane treated silica fillers such asthose disclosed and claimed in copending application Ser. No. 789,352 ofSmith, filed Jan. 6, 1969, are particularly suitable for use in the RTVcomposition of the present invention; and when used, generally, may bepresent in an amount of from about 5 to about 200 parts filler per 100parts of silanol chain-stopped polydiorganosiloxane.

In addition to the modification of the RTV composition of the presentinvention by addition of a metal salt, cure accelerator, fillers ormixtures thereof, the composition of this invention may also be modifiedby the incorporation of various flame retardants, stabilizing agents andplasticizers such as siloxane fluids. Suitable flame retardants includeantimony oxide, various polychlorinated hydrocarbons and organicsulfonates.

Where the compositions of the present invention contain components otherthan the silane and the polydiorganosiloxane, the various ingredientsmay be added in any desired order; however, for ease of manufacturing,it is often convenient to form a blend or mixture of all of thecomponents of the room temperature vulcanizing organopolysiloxane exceptthe silane, to then remove moisture from the resulting mixture bymaintaining the mixture under vacuum, and thereafter to add the silaneprior to packaging of the composition in containers protected frommoisture.

The RTV composition of the present invention is particularly adapted forcaulking and sealing applications where adhesion to various surfaces isimportant. For example, these materials are useful in household caulkingapplications and industrial applications such as on buildings,factories, automotive equipment and in applications where adhesion tomasonry, glass, plastic, metal and wood is required. I The silanes ofthe present invention, i.e., those represented by Formula 1 are made bythe following general procedure. The first step of the procedureinvolves reacting a silane with an acetylenically unsaturated ester viathe following SiI-I-acetylene addition reaction to produce the followingcomposition,

si (R- :-o),R' (Ri .-om)dsi(x In the above formulas, R, R R R afb, c, dand e are as above defined, R is an acetylenically unsaturated radicalhaving from about 3 to about 8 carbon atoms selected from the groupconsisting of acetylenically unsaturated hydrocarbon radicals and halo,nitro and alkoxy-substituted acetylenically unsaturated hydrocarbonradicals, X is selected from the group comprising an acyloxy radical ofthe formula where R is as previously defined or a halogen radicalselected from the group consisting of F, Cl, Br and I; and the sum ofa+b has a value of 1 to 3. The reaction may be catalyzed by a platinumcompound or a platinum complex catalyst. Both the platinum compoundcatalysts and the platinum complex catalysts are well known in the artand are described among other places in US. Pats. 2,923,- 218Speier,3,l59,601-Ashby, 3,159,662-Ashby, and 3,220,972Lamoreaux.

When product purity is essential, the acetoxyalkenyltrihalosilane may beprepared first, then purified and then acetylated. It is much easier topurify the halosilane than the corresponding acyloxy-substituted silanefbecause the halosilane does not have the tendency to condense that theacyloxysilanes may have at higher temperatures and thus may be morereadily purified by distillation.

Examples of compounds of the formula-R-C--O,,R which can be employed inthe above reaction include the following:

o nozc-cm-o-ii-on,

o nogc-crncnlcnzo-ii-cna O rrozo-ornom-o- -onzcna I O HC-CECH-CHzO-iL-CEB I 0 ti --CHPO CH When X of Formula 3 is a halogenradical, acyloxy and/or alkoxy groups can be added to the compositionformed by a variety of techniques any of which are suitable. Thetechniques which can be employed are generally set forth in US. Pat.3,296,195 of Goossens which issued Jan. 3, 1967. As a first technique,the silane of Formula 3 can be reacted with acetic anhydride to producea corresponding acetoxysilane or polyacetoxysilane plus acetyl chloride.The'acetoxysilane or polyacetoxysilane is then reacted with the desiredalkanol or halogenated, nitro or alkoxy-substituted alkanol in the ratioof one mole of alkanol for every mole of silicon-bonded acetoxy groupsthat it is desired to replace. The product is then fractionallydistilled to yield the desired product or a mixture of desired products.Alternative processes are set forth in the above-mentioned Goossenspatent which is hereby incorporated reference.

Examples of carboxylic acid anhydrides which may be employed in theabove reaction include acetic anhydride, propionic anhydride, mixedanhydrides such as acetic propionic anhydride, a-chloro acetic acidanhydride and trifluoroacetic acid anhydride.

Examples of alkanols which may be employed in the above-describedprocess include t-butyl alcohol, t-amyl alcohol, methanol,ethylenecyanohydrin, ethylene chlorohydrin, beta-nitroethanol, ethanol,sec-butanol, and methoxy-ethanol.

The preferred group of silanes which may be employed as cross-linkingagents, chain extending agents and modulus improving agents in an RTVcomposition of this invention are those within the scope of the formulabelow, wherein all Rs and subscripts are as described previously.

When the silane is employed as a cross-linking agents, a has a value of3 and the more preferred silanes are When it is desired to have a chainextending agent employed in combination with the cross-linking agent, a

1 1 has a value of 2 resulting in the silane being difunctional.Preferred difunctional silanes are The presence of a chain extendingagent results in a final cured product having a higher degree ofelasticity. The same result generally may be obtained by using a highermolecular weight silanol-stopped fluid; however, the use of such ahigher molecular weight silanol-stopped fluid may result in a curablecomposition having a much higher viscosity than is desired.

When it is desired to improve the modulus of elasticity, a silane ofFormula 1 wherein a has a value of one is incorporated into the RTVcomposition. The preferred silanes for this application are CH; CH;cit-ll- The use of these monofunctional silane chain-terminating unitsin combination with the cross-linking and optionally chain extendingsilanes discussed above, not only results in a higher modulus ofelasticity but in many instances also improves the adhesion of the curedcompositions to a substrate.

The adhesion of RTVs, cross-linked, chain-extended and chain-terminatedby use of the above silanes, to specific substrates such as aluminum canbe improved markedly by having one or more tert-alkoxy groups as siliconsubstituents. The t-butoxy groups are preferred.

The preferred silanol chain-stopped polydiorganosiloxanes to be used incombination with the silane crosslinking agent described above aresilanol chain-stopped polydiorganosiloxanes having a viscosity in therange of about 100 centipoises to 50,000 centipoises at 25 C. Thepreferred polydiorganosiloxanes are polydimethylsiloxanes having fromabout 10 toabout 15,000 dimethylsiloxy units per molecule and maycontain some t-butoxy groups. The presence of such tertiary alkoxygroups such as t-butoxy groups also improves the adhesion of the RTVs ofthe present invention.

Generally speaking, in a preferred embodiment of the present invention,R is an alkyl radical of not more than 4 carbon atoms, R is an alkylradical of not more than 4 carbon atoms, R is a t-butyl radical, R is anolefinically unsaturated divalent hydrocarbonradical of not more than 5carbon atoms, at least 50% of the groups represented by R and R aremethyl radicals, the remainder being phenyl and n is a number from 10 to50,000.

When adhesion to an oxide film containing substrate is desired,di-t-butoxy-diacetoxysilane may be added to the =RTV composition. Theamount added may vary from 0.2 to 6.0 parts by weight based upon theweight of the silanol-stopped fluid.

Preferred silanes used in the RTV composition described in the presentinvention contain on the average of from 2.05 to 3 silicon-bondedacetoxy groups per silane when a fluid containing two silanolend-stopper is employed. If the number of acetoxy groups were to be two,this would merely result in a build-up of chain length. Average in thissituation means the total number of silicon-bonded acetoxy groupsdivided by the total number of silane molecules used in the RWcomposition. The number, of course, can drop below two when the silanol-12 stopped polydiorganosiloxane contains more than two silanol groupsper molecule. This occurs when there is chain branching in thepolydiorganosiloxane and no chain stopping with non-reactive groups suchas t-butoxy groups or alkyl groups. p v p The preferred RTV compositionof the present invention includes a tin catalyst such asdibutyltindilaurate or tin 'octoate.- For deep section cure, a preferredcatalyst is basic, dimethyltinoleate.

A preferred RTV composition of the present invention also includes afiller, the most preferred of which is the silazane treated silicafiller disclosed and claimed in application Ser. No. 789,352 of Smith,filed Jan. 6, 1969. A filler preferably may be used in an amount of fromabout 10 to about parts of filler per 100 parts of the silanolchain-stopped polydiorganosiloxane.

The silazane treated filler'may be prepared by the following procedure.A fumed silica filler is contacted with ammonia for about. 1% hours at25 C. with agitation. Hexamethyld isilazane is added to the treatedfiller in an amount of about 20 parts per 100 parts of treated fillerand the mixture is heated at about 130 C. for about 2 hours. Water in anamount of about one part by weight is added to the mixture and heatingis continued at 130 C. for an additional hour. The treated silica filleris then purged with N; at 130 C. until the NH content is 50 p.p.m.

The following examples are illustrative of the practice of the presentinvention and are not intended for purposes of limitation. All parts areby weight. The SiH-acetylene addition catalyst which was used in thefollowing examples was prepared according to the teachings of Example 1of U.S.'Pat. 3,229,972 of Lamoreaux, and the catalyst was dissolved inoctyl alcohol to a concentration of 3.8% of platinum (as metal) basedupon the total weight of the solution. The catalyst solution willhereinafter be referred to as catalyst.

EXAMPLE 1 A reaction flask was equipped with stirrer, thermometer,reflux condenser and addition funnel. To the flask was charged 343 partsof propargyl acetate and 3 parts of thE. catalyst. The resultingsolution was heated to 60 C., then 521 parts oftrichlorosilane was addedslowly over a 10 hour period with gentle stirring. The rate of silaneaddition and external heating was adjusted such that the reactiontemperature steadily increased from 60 C. to C. during the 10 houraddition time. Following completion of the addition reaction, the crudereaction mixture was transferred to a distillation apparatus.Distillation at reduced pressures yielded 770 parts of the desiredadducts boiling at 68-74 C./7 mm. Hg. (Found-45.7% hydrolyzable Cl;theory-45.6% Cl.) Gas chromatographic analysis of the product indicatedthat two components were present. Since the Cl analyses were inagreement with the formula H7C5Si0g013, the two components correspond tothe isomeric adducts:

O (Cl;SiCH=CHCHzO 1011 l A small amount of the isomeric adduct is alsopresent. The flask was equipped with thermometer, magnetic stirrer anddistillation head with condenser. The chlorosilane was treated with 408parts of acetic anhydride and upon stirring a mild exotherm was noted.The mixture was heated to reflux and acetyl chloride removed bydistillation to a reaction mixture temperature of 100 C. Gaschromatographic analysis of the mixture indicated that acetylation wascomplete. The remaining volatile components were removed by distilationto a flask temperature of 90 C,. at 12 mm. Hg. The resulting liquidamounted to 281 parts resulting in a 97% yield. The infrared spectrum ofthe material was consistent with the proposed structure. Theacetoxypropenylenyltriacetoxysilane was used to prepare an RTV which wascompared against a control formulation.

A base fluid containing the following constituents was prepared bymixing 100 parts of a silanol-terminated fluid containing an average of-810 dimethylsiloxy units of the formula HO H S iO

20 parts of octamethylcyclotetrasiloxane treated fumed silica (thesilica had a surface area of about 200 sq. meters per gram) and parts ofa process aid prepared according to the teachings of US. Pat. 3,382,205.The process aid consisted of 5 mole percent trimethylsiloxy units, molepercent monomethylsiloxy units, 75 mole percent of dimethylsiloxy unitsand contained 0.5 weight percent silanol. The fluid had a viscosity of20 centipoises.

To 100 parts of the base fluid were added 5 parts ofacetoxypropenylenyltriacetoxysilane and 0.07 part ofdibutyltindilauratel A control formulation was prepared using 5 parts ofmethyltriacetoxysilane in place of theacetoxypropenylenyltriacetoxysilane. After curing, the propertiesmeasured were:

EXAMPLE 2 To a reaction-flask containing 103 parts of triacetoxysilaneand /2 part catalyst and heated to 120 C. was added slowly 29 parts ofpropargyl acetate. A very exothermic reaction occurred. The reactiontemperature at times climbed to 220 C. When the addition of propargylacetate was complete, the reaction mixture was heated to 120 C. for 3hours. Gas chromatographic analysis (VTC) of the mixture showed thepresence of a high boiling adduct with very little starting materialremaining. Upon distillation of the reaction mixture, a fraction with aboling range of 140170 C./ 0.5 mm. Hg was collected. The weght ofproduct was 120 parts.

The product was identified as acetoxypropenylenyltriacetox-ysilane Itspurity by VPC was 98% and the product distilled at 128 C. at 0.4 mm. Hg.The structure was established by its infrared spectrum.

EXAMPLE 3 To a reaction flask containing 252 parts of1,1-dimethylpropargylacetate and 1% parts of catalyst and heated to 95C. was added slowly 271 parts of trichlorosilane. The reaction mixturewas kept at total reflux by external heat. After about 2 hours thereaction temperature began to increase from 46 C. and after 6 hours, thereflux temperature reached 80 C. A gas chromatographic analysis of thereaction mixture at this time showed that an adduct had formed and waspresent in a concentration of about 65% of the reaction mixture. Thereaction was con- 14 tinned until the reflux temperature reached C. andthe reaction mixture was then distilled. The product distilled at 68 to72 C. at 1 mm. Hg. There was obtained 422 parts of product whichanalyzed 98% purity via gas chromatography. The product was identifiedas acetoxydimethylpropenyltlichlorosilane of the formula To a reactionflask was added 152 parts of the acetoxydimethylpropenyltrichlorosilane.The flask was equipped with thermometer, magnetic stirrer anddistillation head with condenser. The chlorosilane was treated with 237parts of acetic anhydride and upon stirring a mild exotherm was noted.The mixture was heated to reflux and acetyl chloride removed bydistillation to a reaction tem perature of 100 C. Gas chromatographicanalysis of the mixture indicated that acetylation was complete.Remaining volatile components were removed by distilation to a flasktemperature of 100 C. at 2 mm. -Hg. The resulting liquid amounted to 186parts resulting in a 96% yield. The infrared spectrum of the materialwas consistent with the proposed structure.

EXAMPLE 4 A reaction flask was equipped with stirrer, thermometer,reflux condenser and addition funnel. To the flask was charged 98 partsof propargyl acetate and 0.6 part of catalyst. The resulting solutionwas heated to 60 C., then parts of methyldichlorosilane was slowly addedwith gentle stirring over a 10 hour period. After the addition wascompleted, the reaction mixture was heated externally to C. Followingcompletion of the addition reaction, the crude reaction mixture wastransferred to a distillation apparatus. Distillation at reducedpressures yielded 195 parts of product at 60 C./ 0.7 mm. Hg. The productwas a mixture of adducts formed by 1 and 2 addition. The productconsisted of 60% of o (011 ((31)2siCH=CH-CH20i JCHi3-acetoxypropenylmethyldichlorosilane and 40% of CH1 0 oH, o1 2si CH20cH,

To a reaction flask was added 106 parts of the two adductsacetoxypropenylmethyldichlorosilane. The flask was equipped withthermometer, magnetic stirrer and distillation head with condenser. Thechlorosilane was treated with 153 parts of acetic anhydride and uponstirring a mild exotherm was noted. The mixture was heated to reflux andacetyl chloride removed by distillation to a reaction mixture of 100 C.Gas chromatographic analysis of the mixture indicated that acetylationwas complete. The remaining volatile components were removed bydistillation to a flask temperature of 90 C. at 12 mm. Hg. The resultingliquid amounted to 120 parts resulting in a 92% yield. The infraredspectrum of the material was consistent with the proposed structure.

EXAMPLE 5 To a reaction flask containing 103 parts of but-Z-yne-1,4diacetate and 0.6 part of catalyst and heated to 75 C. was addedslowly 88.5 parts of trichlorosilane. A mild exotherm took place. Thereaction mixture was heated and the heating maintained throughout thesilane addition. The temperature of the reaction mixture increased to110 C. An additional 0.3 part of catalyst was added and the reaction wasmaintained at total reflux for 2 hours. Upon fractional distillation anadduct distilled at 110 C./ 0.8 mm. Hg. The total yield of product was155 parts. The product was analyzed for hydrolyzable chloride and alsoby infrared spectroscopy which analyses agreed well with the proposedstructure A reaction mixture consisting of 155 parts of the 1,4-diacetoxy-Z-trichlorosilylbutene-2 and 179 parts of acetic anhydridewere combined in a reaction flask and heated at reflux. Acetyl chloridewas removed by distillation. When the temperature of the reactionmixture exceeded 90 C., a vacuum of 10 mm. Hg was applied and acetylchloride and excess acetic anhydride was removed by distillation atreduced pressure. The reaction was terminated when the reaction mixturetemperature reached 110 C. Upon cooling, 50 parts of anhydrous sodiumacetate was added to the reaction mixture. The mixture was then stirredat room temperature overnight. The reaction mixture was filtered and wasshown to be free of chloride by titration with silver nitrate solution.The product was analyzed by NMR and had the structure An RTV compositionwas prepared by mixing at room temperature 100 parts of a base compound,4 parts of acetoxypropenyltriacetoxysilane, 1.5 parts ofdi-t-butoxydiacetoxysilane and 0.05 part of dibutyltindilaurate. Thebase compound consisted of 100 parts of a 10,000 centipoises viscositysilanol-terminated polydimethylsiloxane of the formula Shore A 32Tensile, p.s.i 410 Elongation, percent 420 Tear, lbs./in 40 Tack freetime, min. 10

The tack free time was measured by release from 2 mil polyethylene film.The application rate using a A; Semco orifice at 90 p.s.i. was 385 gramsper minute. The peel adhesion of the above RTV from alclad aluminum was60 pounds per inch. The value was determined using a 20 mesh stainlesssteel screen imbedded in the sealant at a A" bond line. The cure time inthis case was 7 days at 5 0% relative humidity and 77 F.

What is claimed is:

l. A fluid composition stable under substantially anhydrous conditionsand curable to an elastic solid in the presence of moisture whichcomprises a silanol chainstopped polydiorganosiloxane having the formulaR6 SiO HO H 16 10 to about 15,000, and at least one silane representedby the formula wherein R is an alkyl radical of not more than '8 carbonatoms, R is at least one radical having not more than about 8 carbonatoms selected from the, group consisting of hydrocarbyl,halohydrocarbyl, nitrohydrocarbyl, alkoxyhydrocarbyl and cyano loweralkyl and may be different; R and R are at least one radical having notmore than about 8 carbon atoms selected from the group consisting ofhydrocarbyl and halohydrocarbyl and may be difierent; R is at least oneunsaturated radical, attached to the Si through an olefinic carbon atom,having a valence of at least two and from about 3 to about 8 carbonatoms selected from the group consisting of divalent and trivalentunsaturated hydrocarbon radicals, and halo and alkoxy-substituteddivalent and trivalent hydrocarbon radicals; a is an integer of 1through 3, b is a whole number of 0 through 2, c is a whole number of 0through 2, d is an integer of 1 through 3, and e is an integer of 1through 2 and the sum of a, b, c and d is 4.

2. The composition of claim 1 further characterized by at least about50% of the total number of R and R groups being methyl radicals.

3. The composition of claim 2 further characterized by the remaining Rand R groups being phenyl radicals.

4. The composition of claim 1 further characterized by R, R R and,Rbeing alkyl radicals and R being a divalent unsaturated hydrocarbonradical.

5. The composition of claim 1 further characterized by R, R and R beingalkyl radicals, R being a divalent unsaturated hydrocarbon radical and bbeing 0.

6. The composition of claim 1 further characterized by R, R R and Rbeing alkyl radicals, R being a divalent unsaturated hydrocarbon radicaland b being one.

7. The composition of claim 1 further characterized by R, R and R beingalkyl radicals, R being a propenylene radical and b being 0.

8. The composition of claim 1 further characterized by R, R and R beingmethyl radicals, and R being a divalent unsaturated hydrocarbon radical.

9. The composition of claim 1 further characterized by R, R and R beingmethyl, and R being a 3,3-dimethylpropenylene radical.

10. The composition of claim 1 further characterized by at least onesilane being a mixture of silanes of the formula as defined.

11. The composition of claim 10 further characterized by the at leastone silane being a silane represented by the formula mixed with a silanerepresented by the formula 12. The composition of claim 11 furthercharacterized by the at least one silane consisting of a silanebeingselected from the class consisting of 17 mixed with a silaneselected from the group consisting of a silane represented by theformula and a silane represented by the formula 13. The composition ofclaim 12 further characterized by the at least one silane consisting ofa silane being rep resented by the formula and a silane represented bythe formula 14. The composition of claim 1 further characterized by R, Rand R being alkyl radicals, R being a propenylene radical and b beingone.

15. The composition of claim 1 further characterized by R and R beingalkyl radicals.

16. The composition of claim 1 further characterized by R, R, R and Rbeing alkyl radicals and R being a propenylene radical.

17. The composition of claim 1 further characterized by R, R and R beingmethyl radicals and R being a propenylene radical.

18. The composition of claim 1 further characterized by having a fillerpresent.

19. The composition of claim 1 further characterized by having a fillerand catalyst present which is a carboxylic acid salt and/ or chelate ofa metal ranging from lead to manganese, inclusive, in the electromotiveseries of metals.

20. The composition of claim 1 further characterized by having acatalyst present which is a carboxylic ac d salt and/ or chelate of ametal ranging from lead to manganese inclusive, in the electromotiveseries of metals.

21. The composition of claim 20 further characterized by the catalystbeing basic dimethyl tin oleate.

22. The composition of claim 1 when cured to an elastic solid.

23. The composition of claim 1 further characterized by having at leastabout 50% of the organo groups of the silanol chain-stoppedpolydiorganosiloxane being methyl radicals, R and R being alkylradicals, R being a t-butyl radical and R being a propenylene radical.

24. The composition of claim 1 further characterized by having at least50% of the organo groups of the silanol chain-stoppedpolydiorganosiloxane being methyl, R, R and R being methyl radicals, Rbeing a 3,3-dimethylpropenylene radical and b being 0.

25. A method of forming a fluid composition stable under substantiallyanhydrous conditions and curable to an elastic solid in the presence ofmoisture which comprises mixing in the substantial absence of moisture,a silanol chain-stopped polydiorganosiloxane having the formula,

HO 'O about 10 to about 15,000, and at least one silane represented bythe formula,

said silane having an average of at least 2.05 siliconbonded ac'yloxyradicals per silicon atom, wherein R is an alkyl radical of up to 8carbon atoms, and R is a radical having not more than about 8 carbonatoms selected from the group consisting of hydrocarbyl,halohydrocarbyl, nitrohydrocarbyl, alkoxyhydrocarbyl and cyano loweralkyl and may be different; R and R are at least one radical having notmore than about 8 carbon atoms selected from the group consisting ofhydrocarbyl and halohydrocarbyl and may be different; R is at least oneunsaturated radical, attached to the Si through olefinic carbon atom,having a valence of at least two and from about 3 to about 8 carbonatoms selected from the group consisting of divalent and trivalentunsaturated hydrocarbon radicals, and halo and alkoxy-substituteddivalent and trivalent hydrocarbon radicals; a is an integer of 1through 3, b is a whole number of 0 through 2, c is a Whole number of 0through 2, d is an integer of 1 through 3 and e is an integer of 1through 2. and the sum of a, b,canddis 4. a

26. The method of claim 25 further characterized b at least about 50% ofthe total number of R and R groups being methyl radicals.

27. The method of claim 25 further characterized by the remaining R andR groups being phenyl radicals.

28. The method of claim 25 further characterized by R, R R and R beingalkyl radicals, and R being a divalent unsaturated hydrocarbon radical.

29. The method of claim 25 further characterized by R, R and R beingalkyl radicals, R being a divalent unsaturated hydrocarbon radical and bbeing zero.

30. The method of claim 25 further characterized by R, R R and R beingalkyl radicals, R being a divalent unsaturated hydrocarbon radical and bbeing one.

31. The method of claim 25 further characterized by R, R and R beingalkyl radicals, R being a propenylene radical and b being zero.

32. The method of claim 25 further characterized by R, R and R beingmethyl and R being a divalent unsaturated hydrocarbon radical.

33. The method of claim 25 further characterized by R, R and R beingmethyl and R being a propenylene radical and b being zero.

34. The method of claim 25 further characterized by the at least onesilane being a mixture of silanes of the formula as defined.

35. The method of claim 25 further characterized by the mixture of asilane represented by the formula mixed with a silane represented by theformula 36. The method of claim 35 further characterized by thecomposition consisting of a silane selected from the class consisting of19 mixed with a silane selected from the class consisting of a silanerepresented by the formula 0 011,-b-0-0H,0H=0Hsi 0( l-0H,

and a silane represented by the formula 0 CH; 0 CH -iL-O-OH=CHSi(O-&OH

37. The method of claim 36 further characterized by the mixtureconsisting of a silane represented by the formula and a silanerepresented by the formula 38. The method of claim 37 furthercharacterized by R, R and R being alkyl radicals, R being propenyleneradicals and b being one.

39. The method of claim 25 further characterized by -R, R R and R lbeingalkyl radicals and R being a propenylene radical.

'40. The method of claim 25 further characterized by R, R and R beingmethyl radicals and R being a propenylene radical.

41. The method of claim 25 further characterized by having a fillerpresent.

42. The method of claim 25 further characterized by having a filler andcatalyst present which is a carboxylic 20 acid salt and/or chelate of ametal ranging from lead to manganese, inclusive, in the electromotiveseries of metals.

43. The method of claim 25 further characterized by having a catalystpresent which is a carboxylic acid salt and/or chelate of a metalranging from lead to manganese, inclusive, in the electromotive seriesof metals.

44. The method of claim 43 further characterized by the catalyst beingbasic dim'ethyl tin oleate.

45. The method of claim 25 further characterized by having at least ofthe organo groups of the silanol chain-stopped polydiorganosiloxanebeing methyl, R, R and R being alkyl radicals, R being a t-butyl radicaland R being a propenylene radical.

46. The method of claim 25 further characterized by having at leastabout 50% of the organo groups of the silanol chain-stoppedpolydiorganosiloxane being methyl, R, R and R being methyl radicals, Rbeing a propenylene radical and b being zero.

References Cited UNITED STATES PATENTS 3,555,051 v1/ 1971 Marsden et al..3 260348 3,474,064 10/ 1969 Hittmair et al. 260-37 3,296,161 1/1967Kulpa 260-18 DONALD E. C'ZAJA, Primary Examiner M. I. MARQUIS, AssistantExaminer US. Cl. X.R.

117 13s.1, 138.8 E; 161-193, 207; 26032.85 n, 33.2 $13, 33.6 SB, 33.8SB, 37 SB 46.5 Y, 46.5 G, 46.5 UA, 825

